It is the purpose of this project to analyze and develop new and difficult systems for cell culture. We are now pursuing intensively a single cell system: culture of cells from the neonatal rat olfactory epithelium (OLFE). The projects involving thyroid gland reconstruction and thyroid cell genetics have been postponed. We hope to continue these timely experiments as soon as our principal collaborator, Dr. F. S. Ambesi, can return to the laboratory. Meanwhile, our progress with the OLFE has been sufficiently exciting during the past year that it has merited our full attention. Using complex media and substrates we have succeeded in culturing several cell types from the OLFE. The mixed, mass cultures of these cells provide an appropriate conditioned medium that has permitted the isolation of clones from 3rd to 6th passage cultures. We have initiated a hybridoma screen using OLFE as antigen and fluorescent anti-mouse IgG staining of frozen sections of OLFE for selection. These results, too, are very encouraging; many of the hybridoma supernates appear to identify small patches of cells selectively in the OLFE. The sensory neurons of the olfactory epithelium are renewed throughout life from a stem cell population. Development of this system would make available the first mammalian neuroblast to neuron cell culture system. It is hoped that basic issues in olfactory sensory physiology can be explored with this system.